A Simulation Study of Specific Absorption Rate With Twisted Loop Antennas

In this study, we analyze the radiation properties of the $1 \lambda$-mode loop antenna and identify the superposition of the tangential magnetic field radiated from the two in-phase electric currents as the dominant source of specific absorption rate (SAR). Increasing the physical distance between the currents does not reduce the peak 10 g -SAR levels as the superposition of the magnetic field always generates a single 10 g -SAR hotspot in the middle of the loop. One potential solution to reduce the 10g-SAR for SAR compliance is the excitation of the two current sources with a $\mathbf{1 8 0}$-degree phase difference, this is achieved by introducing a twist in the loop. The twisted loop has two 10 g SAR hotspots with a lower peak level and also achieves a 50% size reduction.